1. Field of Invention
The present invention relates to a method and apparatus for measuring the area specific resistance of a metal plate, particularly of low resistivity at high temperatures, with negligible change to the original plate properties.
2. Related Prior Art
To measure the area specific resistance of a metal plate at high temperatures, platinum paste, as a contact electrode, is applied on the metallic surface. Platinum paste is however expensive. Moreover, in the temperature range for the measurement, the degree of the sintering of the platinum particles is low so that the resistance of the platinum paste cannot be minimized and that the platinum particles cannot be firmly attached to the metallic surface. Therefore, the precision of the measurement is affected, particularly when the resistance to be measured is very low.
There are alternative measuring methods such as using a platinum mesh, together with platinum paste or alone, or using a mesh made of other noble metal. The platinum paste suffers the above-mentioned drawbacks. The platinum mesh or the mesh made of other noble metal cannot be firmly attached to the plate surface. There is an attempt to firmly attach the mesh to the plate surface by exerting pressure on the mesh against the plate surface. This however could easily damage the plate surface condition like coating or pre-oxidized scale, and induce errors to the measurement. In addition, the contact area between the mesh and the plate surface can not be accurately determined. Therefore, the above-mentioned methods for measuring the metallic area specific resistance cannot meet the need of precise measurement.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.